There is no such thing as 5.1.7 yet.
There is a frequent Testing release that is a pre-5.1.7 snapshot. Usually but not always, these are safe to use and often better than 5.1.6 as several bugs have been fixed.
I put up threads from time to time identifying releases that I have found to be good.
File formats do not change in this fork, so your project can be shared with 5.1.6 users